reeniebeany
starting to spend too much on rocks
Rotary Only
Member since January 2020
Posts: 125
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Post by reeniebeany on Jun 5, 2020 10:30:50 GMT -5
Hey all, I searched the forums some but still have questions about SC vs. AO. Most of the kits I have seen have 1200 Aluminum Oxide as the polish step. www.johnsonbrotherslapidary.com has 1200 Silicon Carbide They also have CPP Polishing Powder that says it is an Alumina base, so I am guessing it is AO. (No Grit size listed.) I understand that SC breaks down to sharp bits and AO to more rounded bits. Does that mean you would not get shiny if you use SC instead of AO for stage 4? I am rotary, not vibratory.
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Post by knave on Jun 5, 2020 11:41:48 GMT -5
Fully broken down sc can result in a pre-polish, but I’ve not seen a polish from it. Even 500 AO will result in a mirror polish if you run it long enough.
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Post by aDave on Jun 5, 2020 11:44:42 GMT -5
1200 is not polish, despite what the label says. For tumbling, it would be considered a pre-polish, as polish grit size is most often 13,000 to 14,000 (1.5 to 1 micron).
You have correctly identified the properties of AO versus SiC grits, and since SiC tends to cut more than it smooths, most here use AO material later in the tumbling runs. You mention a "stage 4," but because of the different ways people refer to the steps they go through, it's hard to know if where one may be in their process. So, I'll leave you with an example of grits that are common in what "I" might know as a four step process. Note: These grit sizes aren't absolute, but they should give you a decent idea of what a common recipe might look like.
Coarse Stage 60/90 SiC Medium Stage 120/220 SiC Fine Stage 500 AO Polish Stage 13,000 to 14,000 AO
If you chose to use your 1200 AO in the process, it would be between the Fine and Polish stages.
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reeniebeany
starting to spend too much on rocks
Rotary Only
Member since January 2020
Posts: 125
|
Post by reeniebeany on Jun 5, 2020 13:40:21 GMT -5
Thanks! That is very helpful.
My kits have come with:
60/90 Graded Silicon Carbide Grit (Step 1) 120/220 Graded Silicon Carbide Grit (Step 2) 500/600 Graded Silicon Carbide Grit (Step 3) 1200 Aluminum Oxide Polish (Step 4)
I am guessing I got decent shine on my polish step because I left them for several weeks.
It is sure fun to see the results! Some that I tossed in as "maybe ok" turned out to be very cool. I need more work on separating the hardness into batches.
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Post by aDave on Jun 5, 2020 16:02:49 GMT -5
Thanks! That is very helpful. My kits have come with: 60/90 Graded Silicon Carbide Grit (Step 1) 120/220 Graded Silicon Carbide Grit (Step 2) 500/600 Graded Silicon Carbide Grit (Step 3) 1200 Aluminum Oxide Polish (Step 4) I am guessing I got decent shine on my polish step because I left them for several weeks. It is sure fun to see the results! Some that I tossed in as "maybe ok" turned out to be very cool. I need more work on separating the hardness into batches. Your multiple week polish stage with the 1200 probably helped some, but I can guarantee your results will be much better with a "real" polish in a grit size near what I noted above. If you go to a place like the Rock Shed for polish, you'll wind up with AO polish that is 13,000 (even though size is not mentioned). You can also pick up additional grit to your liking, and the prices are about as reasonable as you will find online. Just to give you an idea of what is possible with a rotary (and AO polish from the Rock Shed) here's a batch I did some time ago. Polish stage here was three weeks, and all rocks were around a 7 or higher in hardness.
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